In recent years, regarding a compressor used for a freezing device such as a freezer or a refrigerator, it is required to obtain high efficiency for reducing power consumption, low noise, and high reliability.
In the past, this kind of compressor adopts a thrust ball bearing for the purpose of efficiency improvement so that a shaft is rotatable with respect to a main bearing (for example, see Patent Document 1).
Hereinafter, a general compressor will be described with reference to the drawings. FIG. 10 is a longitudinal sectional view showing a general compressor disclosed in Patent Document 1. A hermetic container 1 accommodates an electric element 2 including a stator 52 and a rotor 54 and a compressing element 4 rotationally driven by the electric element 2 while being disposed beneath the electric element 2, and a lubricant 6 is filled in a bottom portion thereof. The electric element 2 is integrally formed with the compressing element 4 to form a compression mechanism 8, and the compression mechanism 8 is elastically supported to the inside of the hermetic container 1 by a plurality of coil springs (not shown).
A cylindrical compression chamber 22 is formed in a cylinder block 20 forming the compressing element 4, and a piston 24 is fitted to the inside of the compression chamber 22 so as to reciprocate. A bearing 26 is fixed to the upper portion of the cylinder block 20, and a thrust surface 28 is formed on the bearing 26.
A shaft 30 includes a main shaft portion 34 axially supported to the bearing 26 in a vertical direction and having a spiral oil-feeding groove 32 formed in the outer periphery and an eccentric shaft portion 36 formed therebelow. The eccentric shaft portion 36 is connected to the piston 24 via a connection mechanism 44.
Additionally, a pipe-shaped oil filling pipe 42 is press-inserted into an oil-feeding hole (not shown) formed in a lower end 38 of the eccentric shaft portion 36 so that one end of the oil-feeding pipe 42 is communicated from the oil-feeding hole to the spiral oil-feeding groove 32.
The electric element 2 includes a stator 52 fixed to the upper portion of the cylinder block 20 and a rotor 54 fixed to the main shaft portion 34 of the shaft 30 by shrinkage fitting.
It is assembled so that a center position of a rotor iron core 53 of the rotor 54 is substantially identical with that of a stator iron core 51 of the stator 52 in a height direction.
Additionally, FIG. 11 is an enlarged view showing a main part of the general compressor. A thrust ball bearing 60 includes a plurality of balls 62, a holder portion 64 for holding the balls 62, and upper and lower races 66 and 68 disposed on and beneath the balls 62. The upper race 66 comes into contact with a bore plane 58 in a counter bore 56 as a concave portion of the rotor 54, and the lower race 68 comes into contact with the thrust surface 28 of the bearing 26. The plurality of balls 62 roll while coming into contact with the upper race 66 and the lower race 68.
Hereinafter, an operation of the compressor with the above-described configuration will be described.
When a current is supplied from an external power source to the electric element 2, the rotor 54 rotates. In accompany with the rotation, the shaft 30 rotates, rotation motion of the eccentric shaft 36 is transmitted to the piston 24 via the connection mechanism 44, and then the piston 24 reciprocates in the compression chamber 22, thereby enabling the compressing element 4 to perform a predetermined compression operation.
Accordingly, a refrigerant gas is sucked from a refrigeration system (not shown) into the compression chamber 22 to be compressed therein, and is again discharged to the refrigeration system.
At this time, the oil-feeding pipe 42 feeds the lubricant 6 by a centrifugal force so as to lubricate each slide movement portion (not shown), and a part of the lubricant is supplied from the spiral oil-feeding groove 32 to the thrust surface 28 so as to lubricate the thrust ball bearing 60.
The weight of the rotor 54 and the shaft 30 is supported by the thrust ball bearing 60. Since the ball 62 rolls between the upper race 66 and the lower race 68 upon rotating the shaft 30, a torque for rotating the shaft 30 becomes smaller than that of a thrust sliding bearing. For this reason, since it is possible to reduce a loss in the bearing, an input is reduced, thereby obtaining a high efficiency.
However, in the above-described general configuration example, a slide between the ball 62 and the lower race 68 forming the thrust ball bearing 60 or a slide between the lower race 68 and the thrust surface 28 of the bearing 26 coming into contact with the lower race 68 may cause an abrasion of the thrust surface 28 of the bearing 26, the ball 62, and the lower race 68.
Additionally, the abrasion of the thrust surface 28 of the bearing 26, the ball 62, and the lower race 68 may cause an increase of an input of the compressor to thereby deteriorate the efficiency or abrasion powder may be moved by each slide movement portion together with the lubricant 6 to thereby deteriorate the reliability.
[Patent Citation 1]
    Japanese Patent Unexamined Publication No.Sho61-53474